Trailer- or body-mounted agricultural feed delivery systems, also referred to as feed delivery units, are used to transport agricultural feed. The feed delivery unit includes three main delivery augers, namely a floor auger, a vertical auger, and a discharge auger, which are operated simultaneously to transfer feed from the bulk bins of the unit to a receiving bin at the site. In a typical unloading operation, the floor auger transfers feed from the bulk bins towards the rear of the unit, the feed then transitions to the second or vertical auger. The vertical auger transfers the feed from the bottom transition vertically to the discharge auger. The discharge auger then transfers the feed from the top of the vertical auger (near the top of the unit) to the location of the receiving feed bin.
Hydraulic components of a typical trailer- or body-mounted agricultural feed delivery system, interchangeably referred to as a feed delivery unit, typically include a power take-off (PTO), tandem fixed or variable displacement hydraulic pump, a hydraulic control valve, and three hydraulic motors. The system utilizes the tractor engine power and transfers this power via the PTO and hydraulic tandem pump to power the three hydraulic motors, which hydraulically drive the three main augers in the feed delivery unit. Additional augers and hydraulic motors may be used in specialty applications.
In conventional hydraulic systems of feed delivery units, one pump of the tandem PTO driven hydraulic pump drives and is dedicated to the floor auger and the second pump drives and is dedicated to the vertical auger and the discharge auger in a split circuit (i.e., flow from each pump always remains in a separate circuit with no opportunity to combine flow between pumps). The second pump may be plumbed such that it drives the individual motors which power the vertical and discharge augers in series, that is, the outlet from one motor feeds the inlet of the other motor. Alternatively, the second gear pump may be plumbed so that it drives the two motors powering the vertical and discharge auger in parallel, that is, the flow from the second pump is divided, e.g., using a flow divider and/or a directional flow control valve, between the two motors. In either case, conventional systems typically have two distinct pumps plumbed in two distinct circuits, with one pump dedicated to the floor auger and the other pump dedicated to the vertical and discharge augers. In this type of system, excess flow from one pump cannot be shared with other functions and is sent to tank as wasted energy, resulting in low productivity, elevated oil temperatures and premature component failure.
Additionally, feed delivery units are also typically equipped with the functionality to position the discharge auger over the receiving bin, which functionality is typically split into a lift/lower function and a swing function. Typically, these functions do not operate at the same time as the auger functions and therefore could be powered by either of the first or second pumps. FIG. 1 shows a hydraulic diagram of a conventional hydraulic system 10 of a feed delivery unit, in which the pumps are labeled as 12 and 14, the control valve is labeled as 20, and the motors are labeled as 32, 34, 36, and 38. In the system in FIG. 1, the lift/lower function and the swing function are powered by the same pump as the vertical and discharge augers.
The inventors have recognized a number of shortcomings in existing hydraulic systems for feed delivery units. For example, there is variability in the flow rates provided by conventional systems, which can impact performance and productivity. Available hydraulic flow rate from the pump can vary depending on PTO ratio, set engine rpm, pump displacement and pump efficiency. The input flow typically ranges from 40-60 GPM (or 20-30 GPM per pump), but in some cases can be less than or greater than the range stated. To initiate the operation of the hydraulic system, the operator engages the PTO and sets the engine speed corresponding to the desired hydraulic flow rate. The PTO drives the hydraulic pump providing flow to the hydraulics on the feed delivery unit. The flowrate is therefore dependent on the engine speed, PTO ratio, pump displacement and pump efficiency which could all vary from truck to truck and on the truck itself over time. As a result, feed units operate with differing flow rates, impacting performance, productivity, and component durability.
To functionally handle the pump flow from this two-pump system and to split the circuit, a conventional hydraulic control valve typically has two inlets 23, 25 and one outlet 27. The first inlet 23 feeds the floor circuit 22 with one pump of the tandem pump (i.e., pump 12) and the second inlet 25 feeds the vertical/discharge circuit 24 with the other pump (i.e., pump 14). The lift and swing functions are on one of the two circuits, in the illustrated example on the vertical/discharge circuit 24, and as described previously are operated when not operating the augers. A conventional hydraulic control valve such as the one illustrated in FIG. 1 generally keeps each pump separated, combining the flow in the outlet 27 to return to tank. The valve is typically of an open center design sending any unused flow back to tank 8, as shown in FIG. 1.
During operation of such conventional system, the floor auger can provide more feed to the vertical/discharge circuit than the vertical/discharge augers can transfer from the unit. When this happens the flow of feed can become blocked and raise the hydraulic pressure in the auger circuits until the system stalls. Common industry accepted hydraulic solutions implemented to prevent feed blockage include adding additional valves to the circuit and either manual operator input or automatic pressure sequencing to reduce the floor auger speed. If operator input is required, the operator manually adjusts a separate flow control valve controlling hydraulic flow rate to the floor auger motor. This allows the operator to restrict the flow to the floor auger which dumps excess flow to tank. The operator must adjust the valve during operation by observing the pressures in the vertical/discharge circuit. If the pressure on the vertical/discharge circuit rises above an acceptable value, the operator reduces the flow rate to the floor to slow it down. In addition, the operator typically needs to adjust the flow control as the oil heats up during operation. Thus, conventional systems are heavily dependent on a skilled operator paying close attention to system pressures and temperatures.
If automatic functionality is required to slow the floor auger to prevent feed blockage, then a separate hydraulically-piloted sequence valve is added to the circuit. The sequence valve opens once the vertical/discharge pressure reaches a pre-determined value. The sequence valve then dumps a set amount of flow from the floor motor to tank. In either case, if the operator manually slows down the floor auger or the sequence valve automatically slows it down, the excess flow diverted from the floor auger to tank is wasted energy, reducing productivity and increasing the hydraulic oil temperature.
Existing hydraulic systems also rely on the operator to set the truck engine RPM (e.g., cruise control) at the correct speed which is typically around 1000-1200 RPM. Feed delivery units today have few safeguards to prevent the operators from running the hydraulic system at excessive engine speeds. If the operator sets the engine RPM above the specified setting, such as 1500 RPM, for example, a hydraulic system designed for 60 GPM now has 80 GPM flow rate. This excess flow rate creates heat and over-speed conditions causing premature failures of the hydraulic components and degradation of oil lubricity properties which causes further wear of the components and ultimately reduces the system durability.
Thus, improvements and safeguards to existing hydraulic systems for feed delivery units may be desirable.